Apparatus for measuring the refraction characteristics of ophthamological lenses

ABSTRACT

An apparatus for measuring the refraction characteristics of ophthalmological lenses comprises a projection optic for projecting light of a light source via a field aperture with a measuring figure and the ophthalmological lens arranged on a lens support onto a light reception means, the refraction characteristics of the ophthalmological lens being determined from the image site of the measuring figure in at least one direction. The apparatus for varying the vergency of the light beam on the object side of the ophthalmological lens between a position in which the refraction characteristics for the object distance are determined infinitely and at least one alterable position in which the refraction characteristics are determined for finite object distances. The lens support is the lens support means being arranged stationary and enables the ophthalmological lens to be definedly raised and positioned diagonally in the beam path, and at least one of a dioptric and prism compensation element is provided for disposition in the beam path of the diagonally arranged ophthalmological lens for enabling adjustment to a specific dioptric measuring range.

The present invention relates to an apparatus for measuring therefraction characteristics of ophthalmological lenses, in which aprojection optic projects the light of a light source via a fieldaperture with a measuring figure and the ophthalmological lens, which isarranged on a lens support, onto a light reception device and therefraction characteristics are determined from the image site of themeasuring figure in the lateral and/or longitudinal direction.

Such apparatuses are also called apex refracting power gauges and areknown in various designs, by way of illustration as automatic apexrefracting power gauges, with which a test object is imaged, asprojection or telescope apex refracting power gauges, etc. Anot-all-encompassing survey of the different possible designs is givenby the article "Gerate zur Messung des Scheitel-brechwertes" inAugenoptik, 1984, pp 67-70 and the article "Aufbau und Funktion vonMeβgeraten zur automatischen Messung des Scheitelbrechwerts" in DeutscheOotiker-Zeitung 3/1980 pp. 9-21.

Prior art apex refracting power gauges usually operate with parallelbeam paths and determine the so-called distance apex refracting power. Aprinciple measurement error arises when measuring multi-focal lenseswith apex refracting power gauges of this type. With regard to this,reference is made to Dr. W. Roos' articles, by way of illustration, inthe Suddeutsche Optiker Zeitung, 1953, or his special print "Uber denStrahlengang im Nahteilvon Zweistarkenglasern". In order to eliminatethis principle measurement error, an apex refracting power gauge hasbeen suggested in which the lens can be rotated about an axial pointlocated 25 mm behind the eye-facing surface. This apex refracting powergauge is briefly mentioned in the article "Brillenglaser mit gleitenderoptischer Wirkung" by Dr. Josef Reiner, in the Suudd Ootikerzeitung,1961, pp 114 ff and, in particular, on p. 116. Such apex refractingpower gauges with a rotatable lens arrangement have not made asignificant impact in practice.

One reason for this is probably the complicated assembly plus theunaltered beam path, still yielding systematical measurement errors,which is intended for measuring the distance apex refracting power.

The object of the present invention is to provide an apparatus formeasuring the refraction characteristics of ophthalmological lenses,which also permits determining the so-called near apex refracting power,to put it more precisely, the effective use-value.

A solution to this object, in accordance with the present invention, andfurther embodiments thereof is defined in the patent claims hereto.

An inventive element is that the beam path of the apparatus can bealtered corresponding to the desired distanCe from the object. When the"distance from the object is infinite", the beam path in mostapparatuses is, however, not necessarily a parallel beam path. Formeasuring the near apex refractive power or the effective use-value, thevergency of the beam path is altered for the infinite distance from theobject in such a manner that it corresponds to the use position. By wayof illustration, in the case of a specific optical build-up of theinvented apparatus, the parallel beam path may be converted into adivergent beam path (near vergency) by moving the projection opticand/or adding supplementary lenses.

In order to hit the ophthalmological lens with this beam path, whichcorresponds to the use-position, the stationary lens support is designedin such a manner that the ophthalmological lens is positioned"diagonally to the beam path" in the beam path corresponding to theuse-position.

The divergence resulting from positioning the ophthalmological lens"diagonally" in the beam path in near apex measurement is compensatedfor by dioptric and/or prism compensation, by way of illustration, alens or a small additional prism.

By this means, without a rotation device, i.e. without moving parts, theeffective use-value of ophthalmological lenses for near distances can bedetermined with an apparatus for measuring the refractioncharacteristics of ophthalmological lenses.

It is particularly advantageous when the dioptric and/or prismcompensation are integrated in the lens support. By this means not onlythe close spacial arrangement between the ophthalmological lens and thedioptric and/or prism compensation is guaranteed, but also the lenssupport and its respective compensation elements may be exchanged in onestep.

The invented embodiment of an apparatus may be combined with verydifferent apex refracting power gauges. The apex refracting powergauges, may be, by way of illustration, projection apex refracting powergauges or even apex refracting power gauges, which measure therefraction characteristics automatically or, at least, displaydigitally.

At any rate, it is advantageous if the sensors detect the vergency ofthe light beam and/or the beam path in the inserted lens support and/orthe inserted compensation elements. By way of illustration, with anautomatic apex refracting power gauge, the output signals of thesesensors can be utilized to correct measurement results corresponding tothe desired near distance. Also in the case of hand-operated apexrefracting power gauges, in which only the display is automatic, thedisplay can be switched to the near apex refracting power by means ofthe output signals of the sensors. At any rate, it is advantageous ifthe prism compensation, by way of illustration, is of variable design inthat a Herschel compensator is provided.

The present invention is made more apparent in the following sectionusing preferred embodiments thereof and with reference to the drawing,

the only figure of which depicts an optical sketch of an inventedembodiment of an apex refracting power gauge.

A lens 1, having positive refracting power, and a lens 2, havingnegative refracting power, form together a collimator for the light of alight source 3, which is not shown in more detail. The vergency of thepencil of light behind lens 2 may, by way of illustration, be altered bymoving lens 1 in the direction of an arrow 11 and/or by exchanging lens2 or by inserting an additional lens, which is not depicted. in the beampath. Not-depicted sensors, which, by way of illustration, detect theposition of lens 1, inform the evaluation unit, which is also notillustrated, which vergency the beam path has during measuring. In thebeam path behind lens 2 is arranged a lens holder or a lens support 4for an ophthalmological lens 5, by way of illustration a bifocal lens.The light penetrating the ophthalmological lens 5 and the lens holder 4is projected by an additional lens 6 onto a not-depicted light receptiondevice.

The lens support 4 is provided with a supporting surface 41 in such amanner that the ophthaLmological lens 5 can be placed on it with itsnear segment 51 in a specific angle of inclination to an optical axis 7.An exchangeable dioptric and/or prism compensation is integrated in lenssupport 4, which, by way of illustration, comprises a prism 42 and/or alens 43, which can be put in the beam path selectively singly orcombined.

Moreover, the lens support is provided with recesses 44, into which thesensors, by way of illustration microswitches, engage. Depending on theposition of the switch, an evaluation unit, which is not depicted indetail, is hit by signals, which inform the evaluation unit of thedesign of the lens support 4 situated in the beam path, that is theangle of inclination of the ophthalmclogical lens and the dioptricand/or prism correcton.

The following table gives, by way of example, the support dimensions,the prismatic side effects and the prism for the preferred embodimentsof invented lens supports for specific dioptric ranges ofophthalmological lenses 4 of the angles of inclination ofophthalmological lenses compared to horizontal lines.

    ______________________________________    dpt-    Support    Angle of  Prismat.  Prism    range   size       inclination                                 side effects                                           cm/m    ______________________________________     -7     2.1        16°                                 -10        0    to                           to     +8                          +10    +10      2,75      22°                                 +11       15    to                           to    +16                          +20    +16     2,9        23,5°                                 +20       20    to                           to    +20                          +25     -8      1,35      9,4°                                 -10       15    to                           to    -14                          -20    -14     0,8        6° -17       20    to                           to    -16                          -22    ______________________________________

In the preceeding section, the present invention has been described, byway of illustration, with reference to a preferred embodiment withoutthe intention of limiting the scope or spirit of the present invention.Many very different modifications are, of course, possible within theoverall inventive idea--to alter the vergency of the light beam and toarrange the lens defined diagonally to the optical axis and toadditionally provide a dioptric and/or prism compensation. Thus manydifferent measures may be carried out to alter the vergency of the beampath.

Furthermore, by way of illustration, the lens support may be designed insuch a manner that its angle of inclination is adjustable and it can beprovided with many different correction elements.

What I claim is:
 1. An apparatus for measuring the refractioncharacteristics of ophthalmological lenses comprising a projection opticfor projecting light of a light source via a field aperture and theophthalmological lens arranged on a lens support means onto a lightreception means, the refraction characteristics of the ophthalmologicallens being determined from an image site in at least one direction,means for varying the vergency of the light beam on the object side ofthe ophthalmological lens between a position in which the refractioncharacteristics for the object distance are determined infinitely and atleast one alterable position in which the refraction characteristics aredetermined for finite object distances, the lens support means beingarranged stationary and enabling the ophthalmological lens to bedefinedly raised and positioned diagonally in the beam path, andcompensation means for the diagonally arranged opthalmological lens forenabling adjustment to a specific dioptric measuring range beingarranged for disposition in the beam path.
 2. An apparatus according toclaim 1, wherein the compensation means comprises at least one of adioptric and prism compensation element.
 3. An apparatus according toclaim 2, wherein the compensation means is integrated with the lenssupport means.
 4. An apparatus according to claim 1 or 3, wherein themeans for varying the vergency of the light beam includes means for atleast one of adjustably positioning at least one element of theprojection optic and at least one supplementary lens for disposition inthe beam path to as to provide a parallel beam path and a divergent beampath to enable measurement of the distance apex refracting and the nearrefracting power, respectively.
 5. An apparatus according to claim 1,wherein the lens support means comprises a plurality of exchangeablelens supports having different angles of inclination, one of theplurality of lens supports being selected for supporting theophthalmological lens in the beam path.
 6. An apparatus according toclaim 1, wherein the light reception means comprises one of a telescopeand a ground glass.
 7. An apparatus according to claim 1, wherein thelight reception means comprises a detector array providing an output toan evaluation means for determining the refraction characteristicstaking into consideration the object vergency of the light beam.
 8. Anapparatus according to claim 7, wherein the detector array includessensors for detecting at least one of the vergency of the light beam andthe positioning of the lens support placed in the beam path, the sensorsproviding an output to the evaluation means.
 9. An apparatus accordingto claim 1, wherein the lens support means includes means for adjustingthe height and inclination thereof and is connectable to thecompensation means.
 10. An apparatus according to claim 1, wherein themeans for varying the vergency of the light beam enables varying of thevergency between a parallel beam for enabling measurement of thedistance apex refracting power and a diverging light beam for enablingmeasurement of the near apex refracting power.
 11. An apparatusaccording to claim 10, wherein the means for varying the vergency toprovide a diverging light beam includes means for disposing at least onesupplementary lens in the beam path.